Hydraulic locking device



Filed April l. 1963 im. NA

mw www) United States Patent Office 3,177,981 Patented Apr. 13, 1965Filed Apr. 16, 1963, Ser. No. 273,464 8 Claims. (Cl. 18S-96) Thisinvention relates to a hydraulic locking device that is adapted toextend and contract to hold two relaltively movable members at selectedpositions relative to each other.

A typical hydraulic locking device of the type to which the inventionpertains comprises a cylinder confining a quantity of hydraulic fluidand a piston dividing the cylinder into two hydraulic chambers, thepiston being mounted on a piston rod that extends through both of thetwo opposite ends of the cylinder.

What may be termed a locking valve controls communication between thetwo chambers and is normally closed to immobilize the piston. Space isalso provided to function as a reservoir for replenishing iiuid incommunication with at least one of the two hydraulic charnbers, thereservoir being adapted to expand and contract to accommodate thermalexpansion and contraction of the fluid in the two hydraulic chambers,

A device of this type is d-isclosed in the Porter Patent 2,922,497,issu@ January 26, 1960, which patent is hereby incorporated into thepresent disclosure by reference. The Porter device is widely used forthe control of a tiltable back rest of a reclining chair in a passengeraircraft.

An increasing need has developed for a hydraulic locking device of thistype that is capable of greater than usual extension, More specifically,the need is for a hydraulic locking device having a greater ratiobetween -its fully extended length and its fully contracted length, sothat either a shorter device may be used for a given length of stroke ora greater stroke may be provided by a device of the usual length.

There is also need for greater reservoir capacity in a locking device ofa given length. With ample fluid in reserve, a device of this type mayoperate for a long service period with no attention whatsoever.

'I'he yhydraulic locking device disclosed in the Porter patent is aprecision device and cannot be produced as economically as devices thatare manufactured to less strict specifications.

A third need, then, lis for a similar device of less expensiveconstruction for lighter loads. For example, reducing the cost makes itpossible to use such devices widely `on're'clining chairs for busses.

The present invention meets these three needs of greater relativestroke, greater reservoirv capacity, and reduced cost, and does solargely by a new construction geometry. In the new construction, one ofthe hydraulic chambers is a chamber in one end of a cylinder and theusual piston rod is omitted to increase the capacity of this chamber.The second' hydraulic chamber comprises a pair of substantiallycoextensive, interconnected concentric annular compartments, the totalcross-sectional area of which is substantially equal to thecross-sectional area of the lirst chamber. The reservoir for thehydraulic Huid is positioned radially inwardlyfrom the two concentricannular compartments.

The new construction is inherently more economical for a number ofreasons. In the lirst place, the new geometry makes it easier tofabricate and assem-ble the device. In the second place, since thereservoir automatically compensates for any differences that may existbetween the cross-sectional area of the two chambers, liberaldimensional tolerances are permitted. In the third place, the newconstruction may be made of aluminum `tact with the periphery instead ofsteel for light service. As will be made apparent, other features forreducing cost include a novel gland construction for the lluidreservoir, a novel check valve construction and the novel use of rollpins or tubes to serve not only as dowels but also as uid passages.

The various features and advantages of the invention will be apparentfrom the following detailed description and the accompanying drawings.

lIn the drawings, which are to be regarded as merely illustrative z FIG.l is a longitudinal sectional view of the presently preferred embodimentof the invention;

FIG. 2 is an enlarged fragmentary sectional View of a valve arrangementemployed in the device; and

FIG..3 is a transverse section along the line 3 3 of FIG. 2.

Referring `to FIG. 1, the selected embodiment of the invention comprisestwo telescoping structures for attachment respectively .to two membersfor controlling the spacing between the two members. In a recliningchair, one member is the tiltable back rest `and the other member is afixed portion of the chair construction.` One of the two structuresshown in FIG. 1 is a single cylinder 10, having an integral ear 12 atits outer end with an aperture 14 in the ear Ato receive a screw or thelike for attaching the structure to one of the two members. The otherstructure comprises an outer cylinder 15 and an inner cylinder 16, bothof which .are connected to an end fitting 18 that has an aperture Ztl toreceive a screw El' the like for attachment to the other of the two mem-1 ers.

The inner cylinder 16 slidingly telescopes into the single cylinder 10and is provided with a circumferential O- ring 22 at its inner end forsealing contact with the single cylinder. The outer cylinder 15 isformed with an inner circumferential lstep 24 at its inner end, and thisstep is provided with an inner circumferental O- ring 25 -in sealingcontact with the outer circumference of the lsingle cylinder 1l). Thesingle cylinder 1G is formed at :its inner end with an outercircumferential step 2S and an inner circumferential step 30, the outercircumferential step `carrying a circumferential O-ring 32 in slidingsealing contact with the inner surface of the `outer cylinder 15 and theinner circumferential step carrying an inner circumferential O-ring 34in sliding sea-ling conof the inner cylinder 16. As indicated in thedrawing, the two steps 28 and Sti are parts of lan annular pistonmounted on the end of the single cylinder 10.

, As heretofore stated, a locking device of this type has two separatehydraulic chambers with normally closed Valve means to control flowbetween the two chambers.

ln this embodiment of the invention, one of -the twov chambers 35 is`formed -by the single cylinder 10 and the inner end of the innercylinder 16. The other of the two chambers comprises a pair ofconcentric annular compartments 36 and 38 which are interconnected by aplurality of radial bores 40 in the wall of the single cyl-inder 10. Theouter annular compartment 38 is defined by the outer cylinder 15, theinner 24 of the outer cylinder, the single outer circumferential step 28of the single cylinder. The other inner annular compartment 36 is -denedby the single cylinder 10, the inner circumferential step 30 of thesingle cylinder, the outer surface of the inner cylinder 16, and anouter circumferential step 42 on the inner end of the inner cylinder. v

Fluid flow between the hydraulic chamber 35, on the one hand, and thetwo interconnected concentric chambers 36 and 38, on the other hand, iscontrolled by valve means associated with a cylindrical valve body 44that is mounted in the inner end of the inner cylinder 16.

circumferential step Y cylinder 1li, and the` throughout its .lengthintersected by a diametrical Abore-- 46 which registers with two`corresponding radial bores 48 in the wall of the inner cylinder 16. Apair of tubular members 50 in the form of so-called roll pins aremounted in the two radial bores 48 andV extend into the diametricalbore- 46. It is apparent that the two tubular members 50 serve a dualVpurpose, sincethey not only function-as. dowelsto anchor. the vvalvebody 44y against longitudinal `movementin the inner cylinder 16, butalso place the axial passage 45 of the valve body in communication withthe inner'annular compartment 36. Av pair of- O-rings ,S1/onoppositesides ot the diametrical bore 46 prevent leakage ow along theperiphery of the valve bodyl 44.; l i v. f' Y The end 'of the axialpassage '45.of the valve body 44 that is directed'ttowards the hydraulicchamber 35,forms a valve seat 52v for a valve member in the form-of alballj 54.j The ball54 is guided by a oating .cagevintthe form of a block55 that has a cylindrical recess 56 for: engagement witlrtheiball. Asmay be seen 'in FIG. 3, the block is cut ,awayon three sides toprovidevthree passages 58 for uid flow past the block. To bias thevalve;ball 54 to its closed position, .a relatively heavy coil springe60 is `confined under compression between the block 55 and a snap vring,62 that is anchored in the end of the inner cylinder 16V. lodging thevalve ball 54 from the valve seat 52 places the hydraulic chamber 35 incommunication with thev two concentriccompartments 36.' and Y38.

The valve ball 54 is controlled by operating rod means that extendsaxially through the inner cylinder 16frorn the end'itting 18.A As shownin FIG. 1, theend fitting 18has .a nipple portionr 63 which is threadedinto theend of the inner cylinder 16. For the purpose of fixing theoutercylinder 15, the end fitting 18 clamps a washer 64 against the endof. the inner cylinder 16, and thisl washeris engaged lfrom its oppositesides by a pair of snap rings 6.5 that seat inY corresponding innercircum ferential grooves of the outer cylinder '15.- A vent to theatmosphere from the annular space 66 may bevin the form of one or moreapertures 67 inthe washer 64.

The end litting` 18 'has an axial bore 68 which com-l municates with theinterior of the inner cylinder 16, andthe endV fitting is further formedwithja transverse-aperture69 Vto accommodate a transverse control lever70 which is mounted on .a pivot 72. y

The operating yrod ymeans 4forl unseating the normally seated yvalveball 54 comprises a long axial rod 74 whichv extends from the operatinglever 70 to the valve body` 44"and a second 'shorter axial rod 75 lwhichis housed in thesaxial passage 45 of the valve body 44. As 'shown inFIG. 2, the long rod 74 may be formed with and end4 portion '76 otreduced .diameter with vthe end portion extending into an axial socket'78 in the shorter lrod 75. It vis apparent that slight clockwiserotation 'of the control lever 70,^as viewed in FIG. 1, will displacethe two interconnected rods v74 and` 75 longitudinally -to the rod 74and an annular spring seat 85 abutting the O,ring.v The .fluid inthereservoir 80 is maintained under confv stant'pressure-vbyea coil spring86 which is `confined under compression between the-'spring seat 85 andthe nippleportion 63 -of the end tting 18.

The second end of the annular fluid reservoirV 80 is defined-bya checkvalve'shown in` FIG. 2, 'the check valve comprising an -ring 88 andthechamfered end It is apparent that Vdis- CII kright to 'dislodge thevalve ball 54 rfrom its lseatto per Y Y mitfree ow between the hydraulicchamber 35and the two annular compartments 36Y and 38 as 'requiredVforor annular shoulder 90 of the short axial rod 75. The O-ring 88 isvconfined -by aback-up ring 92, which,l in turn, is retained by a snapring 94.

If the device is to be used to control a tiltable back rest of areclining chair, Vit is desirable to add a suitable counterbalancespring. For this purpose. a heavy coil spring 95 may surround the outercylinder 1,5 to resist longitudinal ycontraction-of the device. Oneendof the springabuts an annular member 96-that is xedly mounted on theoutergcylinder A1 5, (The other end of the coil spring extends into acylindrical guard 98 in abutmenty withithe. endwall of the guards.' Theend wall of the guard mayabut a suitable-snaplrifng 102.

Under normal conditions, the'coil springI 60- holdsthe; valve ball 54iirrmly on its seat and the check; valve isV closed, the Vchamferedend.90of theshort axial rod 75 compressing and deforming the O-ring 88.More often; than not, the'control lever 70 is only lightly actuated. toonly slightly dislodgethe valve ball 54 from thel valve seatSZ.' Inthose instances the valve ball -isdis-v lodged suciently for flowbetween the chamber-35 and, the two concentric compartments 36 and 38 topermit extension or. contraction Vof the device, but the check valvedoes no open. In other words, the chamfered end. of the Ashort axial rod75 merely lessens its pressure on. the O-ring 88 without retreatingsuidciently to place the hydraulic reservoir in communication with theaxial. passage 45 of the'valve member 44. In other instances, however,the operating lever 7.0` is actuated to greater extent, with VtheresultV that the valve ball 54 is dislodged from its .valve seat and, inaddition, the .check valve is, opened by retreat of the chamfered end ofthe axial, rod 75 from the O.ring .88., Thus, the. check valve .isopened relatively infrequently, but neverthelessis opened. often enoughto. permit the uid in the'chamber. .35 and the two annular compartments36 and;38. to be re. plenished from the reservoir 80.

It isspossible to override the valve'spring 60 by applying sulicientmechanical. force forV extension Yof the. device; li.e.,` for retractionof theY single. .cylinder 10.rela, tive lto the two cylinders .15`and16. When such .an :everriding force is applied, the rise in pressurein ,the-two; annular compartments.36'and 38 forcesathe valve'ball 54 tolretract in opposition tothe spring .60.

y My description in specific detail of the selected'ernbodi ment of theinventionwill suggestvarious changes,sub.f. stitutions, andotherdepartures from my disclosure within the spirit and scope of theappended claims.

Iclaim:

1. In a hydraulic locking device ofthe character. der; scribed forreleasably locking two members at selected spacing relative.y to eachother, the goombination of;

a first structure in the `form of a vsingle cylinder having an outerclosed `end for connection tol one ofsaid twormernbers and havinganinner openend;

a second structure for connectionfto the other of saidT two'mernbers,said second structure including anY outer lcylinder vand an-inner.,cylinlerr-1'edlycon-` neeted thereto, said outer .cylindertelescopingpover- `said `Single cylinder andrsaidinner 1cylinderslidingly telescopinginto the single cylinder with the single cylinderrandthe ,inner cylinder forming a variable vhydraulic chamlber, saidsingle cylinder and said outer and inner .cylinders ,forming ytwoannular .cornfy partments `interconnected through the wall of the singlecylinder, said two compartments together.

functioning as a second variable hydraulic cham-V V-beriofsubstantiallythe-same crossgsectionalV area as the Erst hydraulicchamber; la hydraulic reservoir inside said inner cylinder; passagemeans inV said inner cylinder for communication'between thetwo-hydraulic chambers and for communication between the reservoir andthe two chambers;

2B a locking valve in said pasage means normally closed to cut olicommunication between the two hydraulic chambers; :and control means to`open said locking valve to permit Huid flow between the two chambersfor change in the spacing of the two members.

2. A combination as set forth in claim 1 in which said control meansincludes an Aaxial rod means extending through said reservoir and intosaid passage means; and

'which includes means restricting fow into and out of ythe reservoir,

said restricting means including a circumferential shoulder formed onsaid rod means and a cooperating elastomeric annular member normallyabutting said shoulder. 3. A combination as set forth in claim 1 inwhich said passage means includes:

a body spanning the interior of said inner cylinder, said body havinguid passages therethrough; and

at least one tubular means extending through the wall `of the innercylinder into said body to anchor the -body and to serve as a fluidpassage member to place said two compartments in communication with theinterior of the body.

4. In a hydraulic locking device of the character described forreleasably locking two members at selected spacing relative to eachother, the combination of:

a first cylinder for connection to one of the two members, the cylinderbeing closed at one end and open at the other end, the cylinder'forming'a first hydraul-ic chamber;

a pair of iixedly interconnected cylinders for connection to the otherof the two members, said pair comprising an outer cylinder and an innercylinder, 'said pair of cylinders forming an annular space, said `firstcylinder extending into the annular space;

an annular piston on the end of said rst cylinder in sliding engagementwith said pair of cylinders;

an inner circumferential sealing means carried by the outer cylinder insliding contact with the first cylinder;

an outer circumferential sealing means carried by the inner cylinder insliding contact with the first cylinder, the three cylinders togetherwith said piston forming two varia-bie annular compartments, said rstcylinder being apertured for continuous communication between the twocompartments;

a hydraulic reservoir inside said inner cylinder;

passage means in said inner cylinder for communication 4between saidfirst variable hydraulic chamber and said two annular compartments;

a locking valve in said passage means normally closing off communicationthrough the passage means; and

control means to open said locking valve to permit fluid flow throughthe passage means to permit change in the spacing of the two members.

5. In a hydraulic locking device of the character described forreleasably locking two mem-bers at selected (30 *3 a second structurefor connection to the other of said two members, said second structureincluding an `Out-er cylinder Iand an inner cylinder xediy connectedthereto, said outer cylinder slidingly telescoping over said firstcylinder and said inner cylinder slidingly tele-scoping into the tirStcylinder; vsaid tirst cylinder together with said inner cylinder:forming a hydraulic chamber,

said three cylinders forming a pair of substantially co-extensiveannular compartments in iiuid communioation through the wall of theinner cylinder;

duid passage means for flow communication between said cham-ber and saidtwo compartments through said inner cylinder; and

a locking valve to control ow through said passage means.

6. A combination as set forth in claim 5 which includes opera-ting meansfor operation of said stop valve, said operating means extending throughsaid inner cylinder longitudinally thereof from the outer end of saidsecond structure.

7. In a hydraulic locking device of the character described forreleasably locking two members at selected spacing rela-tive to eachother, the combination of:

a iirst structure in the form of a first cylinder having an outer closedend for connection to one of said two members;

a second structure for connection to the other of said two members, saidsecond structure including an `outer cylinder and an inner cylinderxedly connected thereto, said outer cylinder slidingly telescoping oversaid first cylinder and said inner cylinder slidingly telescoping intothe rst cylinder,

said rst cylinder together with said inner cylinder 1onming a hydraulicchamber,

said three cylinders forming a pair of substantially coextensive annularcompartments in Huid communication through the Wall of said innercylinder;

fluid passage means for iiow communication between said chamber and saidtwo compartments through said inner cylinder;

a manually operable locking Valve to control ow through said passagemeans; and

means in said inner cylinder forming a reservoir for hydraulic liuidunder pressure to replenish the fluid in said chamber and said twocompartments through said fluid passage means.

8. A combination as set forth in claim 7 which iucludes an operating rodextending axially through said inner cylinder to operate said stopvalve; and

in which said reservoir is formed in part by a gland and a cooperatingspr-ing, said gland comprising an O-ring embracing said operating rodand an annular seat for said spring, said annular seat surround- .ingthe operating rod between the O-ring and the spring.

References Cited by the Examiner UNITED STATES PATENTS 3,051,274 8/62Porter 18S-96 ARTHUR L. LA POINT, Primary Examiner. EUGENE G. BOTZ,Examiner.

1. IN A HYDRAULIC LOCKING DEVICE OF THE CHARACTER DESCRIBED RELATIVE TOEACH OTHER, THE COMBINATION OF: SPACING RELATIVE TO EACH OTHER, THECOMBINATION OF: A FIRST STRUCTURE IN THE FORM OF A SINGLE CYLINDERHAVING AN OUTER CLOSED END FOR CONNECTION TO ONE OF SAID TWO MEMBERS ANDHAVING AN INNER OPEN END; A SECOND STRUCTURE FOR CONNECTION TO THE OTHEROF SAID TWO MEMBERS, SAID SECOND STRUCTURE INCLUDING AN OUTER CYLINDERAND AN INNER CYLINDER FIXEDLY CONNECTED THERETO, SAID OUTER CYLINDERTELESCOPING OVER SAID SINGLE CYLINDER AND SAID INNER CYLINDER SLIDINGLYTELESCOPING INTO THE SINGLE CYLINDER WITH THE SINGLE CYLINDER AND THEINNER CYLINDER FORMING A VARIABLE HYDRAULIC CHAMBER, SAID SINGLECYLINDER AND SAID OUTER AND INNER CYLINDERS FORMING TWO ANNULARCOMPARTMENTS INTERCONNECTED THROUGH THE WALL OF THE SINGLE CYLINDER,SAID TWO COMPARTMENTS TOGETHER FUNCTIONING AS A SECOND VARIABLEHYDRAULIC CHAMBER OF SUBSTANTIALLY THE SAME CROSS-SECTIONAL AREA AS THEFIRST HYDRAULIC CHAMBER; A HYDRAULIC RESERVOIR INSIDE SAID INNERCYLINDER; A PASSAGE MEANS IN SAID INNER CYLINDER FOR COMMUNICATIONBETWEEN THE TWO HYDRAULIC CHAMBERS AND FOR COMMUNICATION BETWEEN THERESERVOIR AND THE TWO CHAMBERS; A LOCKING VALVE IN SAID PASSAGE MEANSNORMALLY CLOSED TO CUT OFF COMMUNICATION BETWEEN THE TWO HYDRAULICCHAMBERS; AND CONTROL MEANS TO OPEN SAID LOCKING VALVE TO PERMIT FLUIDFLOW BETWEEN THE TWO CHAMBERS FOR CHANGE IN THE SPACING OF THE TWOMEMBERS.